An image forming apparatus usually prints data to be imaged provided by an information processing unit, such as a computer (a driving device for short in the present disclosure), on a recording medium. Such image forming apparatus can be a photocopier, a printer, a fax machine, or a multi-function peripheral (MFP) which synthesizes the functions of a photocopier, a printer, and a fax machine into a single system.
Generally, upon input of a PRINT command by a user, a printer driver arranged on the driving device would start transforming the user's document data into data to be imaged that can be identified by the image forming apparatus. Such data transformation as described above is usually termed a data rendering procedure. The driving device will not send a data page to be imaged to the image forming apparatus via a print interface until document data on said page is completely rendered. After the image forming apparatus receives the data to be imaged from the interface unit of the driving device, an imaging control unit of the image forming apparatus will parse the data to be imaged and transmit the parsed data to a print engine, which can output the parsed data on the recording medium.
A document usually contains pages of different levels of complexity, and therefore requires different data rendering durations for data of different pages. Generally, a data page of low complexity requires a relatively short data rendering duration, while a data page of high complexity requires a relatively long data rendering duration. Since the driving device will not send a data page to the image forming apparatus until said data page is completely rendered, where a data page is of relatively high complexity and therefore requires a relatively long rendering duration, the driving device will not send any data to the image forming apparatus for a long time. On the other hand, the image forming apparatus is provided with such protection mechanism that if no data are received from the driving device for a long time, the image forming apparatus will make a decision of timeout. As a result, the image forming apparatus will regard any data received as being useless and therefore discard the data, including the data of a current imaging job. In severe conditions, all data pages of high complexity in a user's document will be mistakenly deleted by the image forming apparatus, instead of being normally printed, which is a waste of resources and seriously affects use thereof.